Magneto-generator, method of manufacturing the same and resin molding die assembly for manufacturing the same

ABSTRACT

A magneto-generator, a method of manufacturing the same and a resin molding die for manufacturing the same. In the magneto-generator, a guard ring is omitted with the performance of the magneto-generator being enhanced. The magneto-generator is manufactured by making use of a resin molding die ( 21 ) having an outer peripheral surface ( 21   d ) to be positioned in opposition to an inner peripheral surface of a flywheel ( 11 ) and projections ( 21   a ) provided in the outer peripheral surface ( 21   d ) for holding a plurality of magnets ( 12 ) at predetermined positions, respectively. The magnets ( 12 ) are positioned and held stationarily at predetermined positions by the aforementioned projections, respectively, and spaces defined between the resin molding die ( 21 ) and the inner peripheral surface of the flywheel ( 11 ) are filled with a resin. After hardening of the resin, the resin molding die ( 21 ) is detached from the flywheel ( 11 ).

CROSS REFERENCE TO RELATED APPLICATION

This is a divisional of application Ser. No. 09/962,344 filed Sep. 26,2001, now abandoned; the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a magneto-generator (alsoreferred to as the magnetoelectric generator) for generating electricpower under the action of electromagnetic induction taking place betweenmagnets mounted on a flywheel and an armature winding during rotation ofthe flywheel and a method of manufacturing the magneto-generator. Moreparticularly, the present invention is concerned with a method ofmanufacturing a flywheel provided with a plurality of magnets mounted onan inner peripheral surface of the flywheel.

2. Description of Related Art

For having better understanding of the concept underlying the presentinvention, description will first be made of a conventional flywheeltype magneto-generator by reference to FIGS. 6, 7 and 8, in which FIG. 6is a front view of a rotor of a conventional flywheel typemagneto-generator disclosed, for example, in Japanese Patent PublicationNo. 81437/1994 (JP-A-6-81437), FIG. 7 is a sectional view of the sametaken along the line VI—VI shown in FIG. 6 as viewed in the directionindicated by arrows, and FIG. 8 is a perspective view of a guard ring ofthe conventional flywheel type magneto-generator disclosed in thepublication mentioned above. Referring to the figures, reference numeral1 denotes a flywheel implemented in a substantially bowl-like shape(hereinafter also referred to as the bowl-shaped flywheel only for theconvenience of description), reference numeral 2 denotes four magnetsmounted on the peripheral wall of the flywheel 1 with equidistancebetween adjacent ones in the circumferential direction, numeral 3denotes a guard annulus or ring of a substantially cylindrical shapewhich is adapted to be closely fit onto the inner surfaces of themagnets 2 which are disposed in a substantially annular array, numeral 4denotes resin blocks filled at both sides and between the adjacent onesof the magnets 2 for fixedly securing the magnets 2 and the guard ring 3to the flywheel 1 in a so-called integrated structure, and referencenumeral 5 denotes a hub or boss formed in the flywheel 1 at a centerportion of the bottom wall for coupling the rotor to a rotatable shaft(not shown).

In the rotor of the conventional magneto-generator implemented in thestructure described above, four magnets 2 are disposed with equidistancetherebetween on the inner peripheral surface of the flywheel 1 with theguard ring 3 being tightly fit onto the magnets 2 on the inner sidethereof, wherein the voids or spaces defined between the innerperipheral surface of the flywheel 1 and the outer peripheral surface ofthe guard ring 3 are filled with the resin 4. In this manner, themagnets 2 and the guard ring 3 can fixedly be secured to the flywheel 1through the medium of the resin 4.

FIG. 9 is a perspective view showing another example of the guard ringemployed in the conventional magneto-generator. Further, FIG. 10 is aperspective view showing the state in which magnets are disposed on theguard ring shown in FIG. 9. As can easily be seen from FIG. 9, the guardring 13 shown therein is destined for use in the magneto-generator inwhich a large number of magnets 2 are employed with the width thereof inthe circumferential direction being reduced when compared with thestructure shown in FIG. 8. Further, the guard ring 13 shown in FIG. 9 isformed with projections 13 a for holding the magnets 2 equidistantlyrelative to one another.

In the conventional magneto-generator of the structure described above,the positions of the individual magnets 2 are sustained by means of theprojections 13 a formed in the guard ring 13 until the magnets 2disposed on the flywheel 1 have been fixedly secured to the flywheel 1.In recent years, however, there has arisen a demand for sparing oromitting the guard ring 3 or 13 with a view to reducing the number ofparts constituting the magneto-generator. In this conjunction, it isfurther noted that the presence of the guard ring 3 or 13 increases thedistance between a generator coil of the stator (not shown) and themagnets 2, which is unfavorable for realization of enhanced performanceof the magneto-generator. For this reason, the guard ring 3 or 13 shouldpreferably be omitted.

SUMMARY OF THE INVENTION

In the light of the state of the art described above, it is an object ofthe present invention to provide a magneto-generator of an improvedstructure which allows the guard ring to be unused or omitted whilereducing the manufacturing cost and which can enhance the performance ofthe magneto-generator by diminishing the distance between the magnetsand the generator coil.

Another object of the present invention is to provide a method ofmanufacturing the magneto-generator of the structure mentioned above.

Yet another object of the present invention is to provide a resinmolding die assembly which can be used for manufacturing theabove-mentioned magneto-generator.

In view of the above and other objects which will become apparent as thedescription proceeds, there is provided according to a first aspect ofthe present invention a magneto-generator which includes a bowl-shapedflywheel, a plurality of magnets mounted on an inner peripheral surfaceof the flywheel, a resin filled around each of the individual magnetsfor fixedly securing the magnets to the flywheel as integral partsthereof, and a generator coil disposed within the bowl-shaped flywheelin opposition to the magnets for generating electric power under theaction of electromagnetic induction brought about through cooperationwith the magnets, wherein the magneto-generator is manufactured bymaking use of a resin molding die having an outer peripheral surface tobe positioned in opposition to an inner peripheral surface of theflywheel and projections provided in the outer peripheral surface forholding the plurality of magnets at predetermined positions,respectively, positioning the magnets at the predetermined positions,respectively, filling the resin in spaces defined between the resinmolding die and the flywheel, and detaching the resin molding die fromthe flywheel.

By virtue of the arrangement described above, there can be implementedthe magneto-generator of an improved structure which allows the guardring is omitted and which thus allows the manufacturing cost to bereduced while ensuring enhanced performance owing to decrease of thedistance between the magnets and the generator coil.

Further, there is proposed according to a second aspect of the presentinvention a method of manufacturing a magneto-generator which includes abowl-shaped flywheel, a plurality of magnets mounted on an innerperipheral surface of the flywheel, a resin filled around each of theindividual magnets for fixedly securing the magnets to the flywheel asintegral parts thereof, and a generator coil disposed within thebowl-shaped flywheel in opposition to the magnets for generatingelectric power under the action of electromagnetic induction broughtabout through cooperation with the magnets. The manufacturing methodincludes a resin filling step in which a resin molding die having anouter peripheral surface to be positioned in opposition to an innerperipheral surface of the flywheel and projections provided in the outerperipheral surface for holding the plurality of magnets at predeterminedpositions, respectively, is employed for filling the resin in spacesdefined between the resin molding die and the flywheel while holding themagnets at the predetermined positions, respectively, and a diedetaching step of detaching the resin molding die from the flywheel.

Owing to the features described above, the guard ring can be omittedfrom the magneto-generator and hence the manufacturing cost of themagneto-generator can be reduced while the performance of the generatorcan be enhanced owing to the shortened distance intervening between themagnets and the generator coil of the magneto-generator.

In a preferred mode for carrying out the method described above, each ofthe projections of the resin molding die should be so provided as toextend continuously and axially from a given position at a side of themagnet substantially up to an open end of the flywheel.

With the arrangement described above, the magnets can securely besustained in the circumferential direction, and the magnets can be heldstationarily in a stabilized manner without incurring undesirablerotation or displacement of the magnets. Thus, the manufacturingefficiency can significantly be enhanced.

In another preferred mode for carrying out the method described above,the resin molding die may include a magnet sucking/holding mechanismdisposed interiorly of the die for securing fixedly the magnets on theouter peripheral surface of the resin molding die upon filling of theresin.

With the arrangement described above, the magnets can be heldstationarily in a much stabilized state. Thus, the manufacturingefficiency can further be enhanced.

Furthermore, there is proposed according to a third aspect of thepresent invention a resin molding die for manufacturing amagneto-generator which is comprised of a bowl-shaped flywheel, aplurality of magnets mounted on an inner peripheral surface of theflywheel, a resin filled around each of the individual magnets forfixedly securing the magnets to the flywheel as integral parts thereof,and a generator coil disposed within the bowl-shaped flywheel inopposition to the magnets for generating electric power under the actionof electromagnetic induction brought about through cooperation with themagnets. The resin molding die includes an outer peripheral surface tobe positioned in opposition to an inner peripheral surface of theflywheel, and projections provided in the outer peripheral surface forholding the plurality of magnets at predetermined positions,respectively.

Owing to the arrangement of the resin molding die assembly describedabove, the guard ring can be omitted from the magneto-generator andhence the manufacturing cost of the magneto-generator can be reduced.Moreover, the performance of the magneto-generator can be enhanced owingto the decreased distance intervening between the magnets and thegenerator coil of the magneto-generator.

In a mode for carrying out the invention, each of the projections shouldpreferably extend continuously and axially from a given position at aside of the magnet substantially up to an open end of the flywheel.

With the arrangement described above, the magnets can steadily be heldin the circumferential direction without incurring rotation or the likedisplacement of the magnets. Thus, the magnets can be held in a muchstabilized state, which in turn means that the manufacturing efficiencyof the magneto-generator can correspondingly be enhanced.

In another mode for carrying out the invention, the resin molding dieshould preferably include a magnet sucking/holding mechanism disposedinteriorly of the die for securing fixedly the magnets on the outerperipheral surface of the resin molding die upon filling of the resin.

With the arrangement described above, the magnets can be held morepositively, whereby the manufacturing efficiency can significantly beincreased.

In yet another mode for carrying out the invention, the resin moldingdie for manufacturing the magneto-generator may further include aring-like projection formed around the outer peripheral surface of thedie for supporting the magnets at one end thereof.

In still another mode for carrying out the invention, the resin moldingdie for manufacturing the may further include a plurality of discreteprojections disposed around the outer peripheral surface of the die forsupporting the plurality-of magnets at one ends thereof, respectively.

In a further mode for carrying out the invention, the resin molding diemay be so designed as to cooperate with an outside molding die disposedaround the resin molding die for supporting an open end of the flywheel.

The arrangements mentioned above contribute to holding stationarily themagnets at respective predetermined positions with high reliabilityduring the resin molding process.

The above and other objects, features and attendant advantages of thepresent invention will more easily be understood by reading thefollowing description of the preferred embodiments thereof taken, onlyby way of example, in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the course of the description which follows, reference is made to thedrawings, in which:

FIG. 1 is a perspective view showing a rotor of a magneto-generatoraccording to an embodiment of the present invention;

FIG. 2 is a perspective view showing a resin molding die assembly whichcan be employed for manufacturing the rotor shown in FIG. 1;

FIG. 3 is a view showing the state in which magnets are magneticallyattracted stationarily onto a resin molding die assembly;

FIG. 4 is a perspective view showing another example of the resinmolding die assembly;

FIG. 5 is a perspective view showing yet another example of the resinmolding die assembly;

FIG. 6 is a front view of a rotor of a conventional flywheel typemagneto-generator;

FIG. 7 is a sectional view of the same taken along the line VI—VI shownin FIG. 6 and viewed in the direction indicated by arrows;

FIG. 8 is a perspective view showing a guard ring employed in theconventional flywheel type magneto-generator;

FIG. 9 is a perspective view showing another example of the guard ringemployed in the conventional magneto-generator; and

FIG. 10 is a perspective view showing the state in which magnets aredisposed on the guard ring shown in FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail in conjunction withwhat is presently considered as preferred or typical embodiments thereofby reference to the drawings. In the following description, likereference characters designate like or corresponding parts throughoutthe several views.

FIG. 1 is a perspective view showing a rotor of a magneto-generatoraccording to an embodiment of the present invention. Referring to FIG.1, the rotor of the magneto-generator according to theinstant-embodiment of the invention includes a bowl-shaped flywheel 11which is composed of a cylindrical peripheral wall 11 a and a bottomportion 11 b formed integrally with the cylindrical peripheral wall 11 aso as to close one open end of the cylindrical peripheral wall 11 a.Formed at a center of the bottom portion 11 b of the flywheel 11 is ahub or boss 15 which is employed for coupling the rotor to a rotatableshaft such as e.g. a crank shaft of an internal combustion engine (notshown). Further, twelve magnets 12 each having an arcuate cross-sectionare disposed on the inner peripheral surface of the cylindricalperipheral wall 11 a of the flywheel 11 equidistantly relative to oneanother as viewed in the circumferential direction. Resin 14 is filledin the spaces formed between the individual magnets 12 and at both sidesthereof so that the magnets 12 are embedded flush in the resin 14,whereby the magnets 12 are fixedly secured at respective predeterminedpositions in the axial direction as well as in the radial direction.

FIG. 2 is a perspective view showing a resin molding die assembly whichcan be employed for manufacturing the rotor shown in FIG. 1. The resinmolding die assembly according to the instant embodiment of theinvention is generally comprised of two major portions, i.e., a rotorinside molding die 21 and a rotor outside molding die 22. Provided inthe outer peripheral surface of the rotor inside molding die 21 areprojections 21 a for sustaining or holding the magnets 12 in thecircumferential direction while projections 22 a for holding the magnets12 in the axial direction are provided in the rotor outside molding die22. Each of the projections 21 a extends continuously in the axialdirection from a given position at a side of the magnet (not shown)substantially up to the open end of the bowl-shaped flywheel 11.Further, through-holes 21 b for sucking and holding fixedly the magnets12 are formed in the rotor inside molding die 21 at positions where themagnets 12 are to be positioned. To this end, a magnet sucking/holdingmechanism (not shown) is disposed in the interior of the rotor insidemolding die 21 for sucking and holding stationarily the magnets 12 bymaking use of e.g. a negative pressure or vacuum. By way of example, themagnet sucking/holding mechanism mentioned above may be constituted bysuction or vacuum nozzle devices connected hydraulically to a vacuumsource such as a vacuum pump for sucking the magnets 12 under vacuum byway of the through-holes 21 b to thereby hold stationarily the magnetsat respective positions. Alternatively, the magnet sucking/holdingmechanism may be constituted by a magnetic holding device or the likewhich is designed to magnetically attract the magnets 12 for therebyholding them stationarily at respective positions under magneticattracting force. In FIG. 3, there is shown the state in which themagnets 12 are fixedly disposed in the resin molding die assembly undervacuum or magnetic attraction.

The flywheel rotor is manufactured by making use of the resin moldingdie assembly implemented in the structure described above in the mannerdescribed below. The flywheel to be mounted with magnets, the rotorinside molding die 21 and the rotor outside molding die 22 are mutuallysuperposed such that an end face 21 c of the rotor inside molding die 21is brought into contact with the bottom portion 11 b of the flywheel 11,an outer peripheral surface 21 d of the rotor inside molding die 21 isdisposed in opposition to the inner peripheral surface of the flywheel11, and an end face 22 b of the rotor outside molding die 22 bears onthe opening edge portion 11 c of the flywheel 11, whereby spaces to befilled with resin are formed, respectively. These spaces are then filledwith the resin 14. Thus, the magnets 12 are fixedly secured atpredetermined positions, respectively, after the resin has beenhardened. Subsequently, the resin molding dies are detached from theflywheel 11.

FIG. 4 is a perspective view which shows another example of the resinmolding die assembly. In the case of this resin molding die assembly,the projection provided in the rotor outside molding die 22 for holdingstationarily the magnets in the axial direction is formed in an annularor ring shape such as exemplified by a ring-like projection 122 a.

FIG. 5 is a perspective view which shows yet another example of theresin molding die assembly. In the case of this resin molding dieassembly, projections provided in the rotor outside molding die 22 forholding the magnets in the axial direction are each formed in an arcuateshape, as exemplified by the projections 222 a.

In the magneto-generator implemented in the structure described above,the magneto-generator includes the bowl-shaped flywheel 11, a pluralityof magnets 12 mounted on an inner peripheral surface of the flywheel 11,the resin 14 filled around each of the individual magnets 12 for fixedlysecuring the magnets 12 to the flywheel 11 as integral parts thereof,and a generator coil disposed within the bowl-shaped flywheel 11 inopposition to the magnets 12 for generating electric power under theaction of electromagnetic induction brought about through cooperationwith the magnets 12. The magneto-generator is manufactured by making useof the resin molding die 21 having the outer peripheral surface 21 d tobe positioned in opposition to the inner peripheral surface of theflywheel 11 and projections 21 a provided in the outer peripheralsurface 21 d for holding the plurality of magnets 12 at predeterminedpositions, respectively, positioning the magnets 12 at the predeterminedpositions, respectively, filling the resin 14 in spaces defined betweenthe resin molding die 21 and the flywheel 11, and detaching the resinmolding die 21 from the flywheel 11 after the resin has been hardened.By virtue of the arrangement described above, there can be manufacturedthe magneto-generator of an improved structure which allows the guardring usually employed in this type conventional magneto-generator to beomitted and hence the manufacturing cost to be reduced. In addition, theperformance of the magneto-generator can significantly be enhancedbecause the distance between the magnets and the generator coil isshortened owing to the absence of the guard ring.

Further, the method of manufacturing the magneto-generator according tothe instant embodiment of the invention includes the resin filling stepin which the resin molding die 21 having an outer peripheral surface 21d to be positioned in opposition to the inner peripheral surface of theflywheel 11 and the projections 21 a provided in the outer peripheralsurface 21 d for holding the plurality of magnets 12 at predeterminedpositions, respectively, is employed for filling the resin 14 in thespaces defined between the resin molding die 21 and the flywheel 11while holding the magnets 12 at the predetermined positions,respectively, and the die detaching step of detaching the resin moldingdie 21 from the flywheel 11. Owing to the features described above, theguard ring usually employed in this type conventional magneto-generatorcan be omitted in the magneto-generator according to the presentinvention and thus the manufacturing cost thereof can be reduced whilethe performance of the magneto-generator can be enhanced because thedistance intervening between the magnets and the generator coil of themagneto-generator is diminished owing to the omission of the guard ring.

Many modifications and variations of the present invention are possiblein the light of the above techniques. It is therefore to be understoodthat within the scope of the appended claims, the invention may bepracticed otherwise than as specifically described.

1. A combination of a magneto-generator rotor and a resin molding die,wherein: said magneto-generator rotor comprises a bowl-shaped flywheel,a plurality of magnets mounted on an inner peripheral surface of saidflywheel, and resin filled around each of said magnets for fixedlysecuring said magnets to said flywheel; and said resin molding diecomprises an outer peripheral surface positioned in opposition to theinner peripheral surface of said flywheel, and projections provided insaid outer peripheral surface abutting against and retaining saidplurality of magnets in a circumferential direction.
 2. A combination ofa magneto-generator rotor and a resin molding die according to claim 1,wherein said plurality of magnets have arcuate cross sections.
 3. Acombination of a magneto-generator rotor and a resin molding dieaccording to claim 1, wherein radially innermost surfaces of the magnetsare flush with radially innermost surfaces of the resin.
 4. Acombination of a magneto-generator rotor and a resin molding dieaccording to claim 1, wherein the resin extends around circumferentialsides, tops and bottoms of each of the magnets.
 5. A combination of amagneto-generator rotor and a resin molding die according to claim 1,wherein a radial thickness of the resin is equivalent to a radialthickness of the portion of the bowl shaped flywheel whereupon themagnets are mounted.
 6. A combination of a magneto-generator rotor and aresin molding die according to claim 1, wherein radially innermostsurfaces of the resin comprise indentations formed by the projections ofthe resin molding die.
 7. A combination of a magneto-generator rotor anda resin molding die according to claim 6, wherein the indentationscomprise grooves extending axially along circumferential sides of themagnets.
 8. A combination of a magneto-generator rotor and a resinmolding die according to claim 1, wherein axially outermost surfaces ofthe resin comprise indentations formed by the projections of the moldingdie.
 9. A combination of a magneto-generator rotor and a resin moldingdie according to claim 8, wherein the indentations comprise holesextending perpendicularly from axially upper surfaces of the magnets.10. A combination of a magneto-generator rotor and a resin molding dieaccording to claim 1, wherein: the bowl shaped flywheel comprises abottom portion and a cylindrical peripheral wall whereupon the magnetsare mounted; and the magnets do not extend axially beyond the peripheralwall.